Fabrication Of A Flexible Polyimide Electrostatically Actuated MEMS Relay

In recent years,flexible electronics based on polymer materials have attracted wide attention,and have been widely used in displays,solar cells and integrated circuits.MEMS(Micro electro mechanical systems)relay plays a role of control,circuit conversion and logic operation in the circuit.It is a core component of electron device.However,the traditional MEMS based on rigid materails such as silicon can not be used in flexible electronics.Therefore,a methold of fabrication of a polyimide-based electrostatically actuated MEMS relay is proposed.The substrate and movable structure are all polyimide,which makes the relay have a good flexibility.Firstly,a series of comparative experiments were carried out on three different types of polyimide photoresists of PW-1500 S,FB-5410 and ZKPI-520.The elastic modulus,hardness,corrosion resistance of different polyimide films were studied after temperature treatment.The adaptability of polyimide films was compared.The resolution and patteren quality of the three polyimide photoresists were compared.The experimental results show that the PW-1500 S polyimide photoresist has good comprehensive performance and can meet the requirements of this experiment.Secondly,the process of film forming of PW-1500 S polyimide photoresist was studied.The relationship between the thickness and uniformity of polyimide film and the rotating speed of the spin coating,the influence of the prebaking parameters on the pattern quality have been studied.The exposure parameters of polyimide precursor were optimized.The development method of polyimide precursor was introduced.The effect of curing parameters on the elastic modulus and hardness of polyimide film was studied.Finally,a four-photomask method for fabricating relays was developed.The processes for patterning the SiO2 sacrificial layer and curing the PI layer for making the movable structure were optimized.The leakage current,pull-in voltage and contact resistance of the relay were tested.Nonoindentor test showed that the hardness of the Au film on the polyimide substrate was 42% of the Au film on the silicon substrate.Obviously,using PI as the substrate of the drain electrode significantly reduced the effective hardness of the contact material.In turn,the decrease of the hardness of the contact material contributed to obtaining a lower contact resistance.The contact resistance of the MEMS relay with a PI substrate was 46% of the MEMS relay with a silicon substrate.